Abstract:

[Objective] This study was conducted to assess the effects of alfalfa cultivation on physiochemical properties of farmland soil and its main driven factors. [Method] A total of 36 published relevant papers indexed in the China National Knowledge Infrastructure （CNKI） database were collected. Using clear tillage as the control, the effects of alfalfa cultivation on physiochemical properties of farmland soil were investigated with the Meta-analysis method. Based on the structural equation model, the impact intensities of meteorological factors and soil physicochemical properties on soil contents of organic carbon, available nitrogen, available potassium, total nitrogen as well as soil moisture content and bulk density were evaluated. [Result] Alfalfa cultivation extremely significantly （P<0.001) increased the farmland soil contents of organic carbon, available nitrogen, total nitrogen, available potassium, and the moisture content by 43.62%, 38.54%, 31.00%, 21.77%, and 21.05%, respectively; significantly （P<0.05) increased the soil available phosphorus content, with an average effect size and an increasing extent of 0.345 ± 0.137 and 41.20%, respectively; extremely significantly （P<0.001) reduced the soil bulk density. With increases of 16.42%, 1.42%, and 1.11%, respectively, alfalfa cultivation also increased the soil contents of total phosphorus and total potassium as well as the soil pH value, however none of these changes were significant （P>0.05). The average annual temperature and precipitation had extremely significant （P<0.001） impacts on the soil organic carbon content in alfalfa cultivation land. [Conclusion] The climate scenario of precipitation increase in the future would significantly increase the soil organic carbon content in alfalfa cultivation land, but global warming would reduce the soil organic carbon content in alfalfa cultivation land.

Key words: alfalfa, soil organic carbon, average effect size, structural equation model